[...] Enjoy your secure economic cold wallet.
That's not a cold wallet.
A cold wallet is defined by a wallet[1] (obviously) which does never touch the internet.
An encrypted USB stick is a place to store your keys at most.
If you insert your stick into your online pc and decrypt it with veracrypt, your keys can be stolen by malware on your computer.
[1] A wallet is defined as soft- and or hardware which manages your private keys and is able to create / sign transactions.
[...] that way you are basically creating a hardware wallet capable of signing transactions offline (that is if you disabled network on that Linux OS).
A hardware wallet needs some sort of a secure element.
An encrypted linux partition with your private keys stored there is not a hardware wallet.
Once plugged in and decrypted, the private keys can be retrieved (which is not possible with a hardware wallet).
This is a sweat idea and relatively secure as long as you can trust the hardware/computer you are plugging your stick into, but not as safe/secure as a hardware wallet.